Deflection system for television receivers



June 22, 1965 MAK EFLECTION SYSTEM FOR TELEVISION RECEIVERS Filed Nov.21, 1961 PRIOR ART FIG. 2

INVENTOR GERRIT MAK AGENT United States Patent 3,191,104 DEFLE-CTIONSYSTEM FOR TELEVISION RECEIVERS Gerrit Mair, Fliuders Park, SouthAustralia, Australia, assignor to North American Philips Company, Inc.,New York, N.Y., a corporation of Delaware Filed Nov. 21, 1961, Ser. No.153,811 Claims priority, application Australia, Nov. 1, 1961, 66,677/ 602 Claims. (Cl. 317-200) The invention relates to a deflection coilsystem for use in television display tubes comprising a screening cap,surrounding the coils, and made of insulating molding material,supporting permanent magnets for image correction.

In known devices of the kind set forth use may be made of rod-shapedcorrection magnets, which are fastened onto the screening cap in suchway that the position of a magnet with respect to the deflection coilsystem may be adjusted. The invention has for its object to provide adevice of the kind referred to above, in which no separate magnets to beadjustably fastened to the cap are needed, so that it may beinexpensive.

In accordance with the invention this is achieved by making the cap atleast partly from molding material including permanently magnetizablematerial. Certain parts of the cap may be magnetized by means of asuitable electro-magnet and are thus capable of fulfilling the functionof correction magnets.

The invention will be described more fully with reference to theaccompanying drawing in which:

FIG. 1 shows a deflection coil system in a perspective view from therear of known construction, in which the invention can be carried out;

FIG. 2 shows the deflection coil system of the invention.

The drawings show an essentially truncated-coneshaped, hood of syntheticresin open at both ends, in which a deflection coil system of knownstructure (for the sake of clarity this is not shown) for the deflectionof the electron beam in a television display tube is arranged. In theknown device of FIG. 1 the front end of the hood 1, Le. the end facingthe image screen of the display tube (not shown) from behind hasarranged in its neighborhood a number of rod-shaped correction magnets 3and two cylindrical, rotatable magnets 7, provided with pole shoes 5. Inaccordance with the invention one or more of these magnets may bereplaced by annular zone 9 near the edge of the hood 1, in which zonethe hood is made "ice of molded material which containspermanent-magnetizable material i.e. particles having a high coerciveforce, for example ceramic material such as barium ferrite, preferablyin the form of a powdery filler. Discrete parts of this annulus, thelocation of which approximately correspond to those of some of themagnets 3, can be magnetized by means of a suitable electro-magnet byarranging the poles thereof on the said zone and passing through themagnet a strong current pulse. The parts thus magnetized can fulfill thefunction of correction magnets. The location of the magnetized zones asshown in FIG. 2 may be determined experimentally by observing theircorrecting effect on the image; if necessary, the magnetizations may beerased and be replaced by magnetizations at other places and so on,until the desired correction of the raster appearing on the display tubeis obtained. Owing to the possibility of varying the magnetization ofthe annulus 9 no magnets need be employed which have to be fastened tothe screening hood 1 so as to be mechanically adjustable, so that thestructure may be made inexpensively.

What is claimed is:

1. In a deflection coil system for television display tubes, a screeninghood of insulating molding material, said screening hood comprising agenerally truncated conical portion for housing deflection coils and anannular marginal portion, said annular marginal portion having adispersion of permanent magnetizable powder of high coercive forcewhereby discrete areas of said annular portion may be permanentlymagnetized for image correction,

2. A deflection coil system for television display tubes, a screeninghood of insulating molding material, said screennig hood comprising agenerally truncated conical portion for housing a deflection coil and anannular marginal portion, said annular marginal portion containing afiller of powdered permanently magnetizable material of barium ferritewhereby discrete areas of said annular portion may be permanentlymagnetized for image correction.

References Cited by the Examiner UNITED STATES PATENTS LARAMIE E. ASKIN,Primary Examiner.

1. IN A DEFLECTION COIL SYSTEM FOR TELEVISION DISPLAY TUBES, A SCREENINGHOOD OF INSULATING MOLDING MATERIAL, SAID SCREENING HOOD COMPRISING AGENERALLY TRUNCATED CONICAL PORTION FOR HOUSING DEFLECTION COILS AND ANANNULAR MARGINAL PORTION, SAID ANNULAR MARGINAL PORTION HAVING ADISPERSION OF PERMANENT MAGNETIZABLE POWDER OF HIGH COERCIVE FORCEWHEREBY DISCRETE AREAS OF SAID ANNULAR PORTION MAY BE PERMANENTLYMAGNETIZED FOR IMAGE CORRECTION.